Idle pulse to 0 and back

Idle pulse to 0 and back

Author
Discussion

igiveup

Original Poster:

2,875 posts

281 months

Thursday 30th June 2016
quotequote all
Some help/advice please...

Went for a drive, stopped off for some fuel (Shell VMax full tank).

Carried on journey and all fine. Get to destination and switch off for s good 30 mins.

Start up and after a min or two it starts doing the following https://youtu.be/9XftbLY59uI

My gut feeling says fuel related possible dirty fuel or crp from bottom of tank has got into fuel filter?

Anyway any help or pointers appreciated

blitzracing

6,387 posts

219 months

Thursday 30th June 2016
quotequote all
Unplug the stepper and see if it will keep idling as on a warm engine it should tick over nicely. This will eliminate anything odd with the ECU. It could be an air leak in the plenum making the mixture unstable when the throttle is shut, or ignition dropping a cylinder as the RPM drops, and the ECU trying to control the idle, leading to that type of cycling.

igiveup

Original Poster:

2,875 posts

281 months

Thursday 30th June 2016
quotequote all
blitzracing said:
Unplug the stepper and see if it will keep idling as on a warm engine it should tick over nicely. This will eliminate anything odd with the ECU. It could be an air leak in the plenum making the mixture unstable when the throttle is shut, or ignition dropping a cylinder as the RPM drops, and the ECU trying to control the idle, leading to that type of cycling.
Thanks will give that a go tomorrow. Actually I did take off the Stepper motor the other day to give it a clean. It has no gasket (Should it?) seems odd to me so i put some PTFE tape around the thread, looked like some had already been applied before too. So maybe that's all it needs?

I'll see if I can find any leak in the plenum.

Thanks.


igiveup

Original Poster:

2,875 posts

281 months

Friday 1st July 2016
quotequote all
Started car from cold, left to idle till it got warm. At about 75c it started to do the above. Unplugged stepper motor and engine settled and ran fine, plugged stepper back in and instantly went back to what it's doing in video. I'll wait for it to cool down again and strip it out.

Thanks for the pointer.

blitzracing

6,387 posts

219 months

Friday 1st July 2016
quotequote all
Its not a Chinese copy stepper by chance?

igiveup

Original Poster:

2,875 posts

281 months

Friday 1st July 2016
quotequote all
I have no idea, it came with the car. It's been fine for the year I've had it, but started playing up yesterday whilst I was doing a school prom ride!! Timing lol

igiveup

Original Poster:

2,875 posts

281 months

Friday 1st July 2016
quotequote all
I've taken the stepper out and given it a clean, wasn't dirty . But put it back in hand tight, used grips last time. It was probably in to tight and not being able to close in tolerance before?

Anyway it seems better now.

Thanks for your help 😂

blitzracing

6,387 posts

219 months

Saturday 2nd July 2016
quotequote all
Ive seen a similar problem on one of the Chinese copies where air was getting past the motor inside the stepper as it was not sealed correctly in its housing.